Gable top cartons have been known for the better part of the twentieth century. Their characteristic simplicity and resealability have helped to sustain their popularity as containers for traditional liquid food products such as milk and juice, but in recent years they have been used for products ranging from ammunition to Epsom salts. Gable top cartons typically start out as generally rectangular carton blanks made of laminated paperboard or similar material. The carton blanks are provided with a number of creases to facilitate folding and forming the blank into a carton.
When fully folded, filled, and sealed, most gable top cartons include a gabled top structure that engages a plurality of side panels. These side panels form a hollow rectangular body. At the end of this hollow rectangular body opposite the gabled top structure, there is a bottom structure.
The bottom structures of the prior art may be formed in accordance with several different constructions. A first construction is shown in U.S. Pat. No. 3,164,315, issued on Jan. 5, 1965 to N. A. Kelly. As illustrated in that patent, the bottom is formed primarily by four bottom panels that engage the side panels at respective straight score lines that each define a straight crease. Two bottom panels each include two converging score lines. The other two bottom panels do not include further score lines. One of the two non-scored bottom panels is longer than the other. When folded, a portion of the longer, non-scored bottom panel overlaps a portion of the opposite non-scored bottom panel to assist in sealing the bottom structure.
Although the bottom structure of the carton disclosed in the '315 patent provides generally adequate sealing, there is room for improvement. For example, the portion of the longer, non-scored bottom panel that overlaps the opposite non-scored bottom panel forms a ridge which does not allow the container to sit flat on a surface. Instead, the ridge tends to form a fulcrum that renders the carton unstable. Such bottom structures are also subject to bulging which renders them relatively unstable when seated. The bottom seal of such a carton is also subject to wear since it is in direct contact with the surface on which the carton is seated. Additionally, depending on the container contents, the bottom structure may require mechanical sealing strength characteristics beyond those offered by the standard four panel structure.
Another bottom construction is shown in U.S. Pat. No. 5,152,736, issued Oct. 6, 1992, to Owen et al. In that construction, the fin flaps of the bottom structure are cut diagonally and engage bottom flaps at diagonal score lines. During the filling and sealing process, the resulting fin is gripped by specialized sealing jaws and forced upward so that the fin does not interfere with seating of the carton. The side panels engage the bottom structure at straight score lines that define straight creases. The fin is then sealed, in a separate sealing step, by folding the fin flat and heat sealing it to one of the bottom flaps of the container.
The '736 construction has several disadvantages. For example, all four side panels engage the bottom flaps at straight score lines that define straight creases. A downward force is thus exerted on the bottom structure by all four panels, as well as the container contents, to urge the bottom flaps and bottom fin flaps from their non-interfering position when the carton is seated upright. As a result, the bottom seal may become unduly stressed and/or move toward an interfering position. Compensation for this added stress may be achieved, for example, by increasing the thicknesses of the heat sealing layers of the container to increase the strength of the bottom heat seal. However, this results in added production costs, particularly when large production volumes are contemplated.
The gabled tops of standard gable top cartons are typically formed primarily from four top flaps that engage respective side panels of the carton at respective straight score lines that each define a straight crease. Two of the top flaps each include two converging diagonal score lines. The top flaps each engage a respective top fin flap that is divided from the top flap by a respective score line. These structures are folded to form the familiar gable structure that includes an upright fin. One end of the gabled structure constitutes an opening end that has its fin flaps sealed, for example, with an adhesive resin. The user inserts his/her thumbs into an open space beneath the fin flaps to pry them apart and access the container contents. The other end of the gabled structure is typically designated as the closed end and is not designed to be opened by the user.
The conventional gabled top structure suffers from disadvantages in certain situations. In particular, miniature gable top cartons may be difficult to open since the open region beneath the fin flaps at the opening end may not be large enough to accommodate the user's thumbs. The requirement that the open region accommodate the user's thumbs also places a constraint on the height of the gabled structure, even where the carton itself is of a conventional size (i.e., 1 liter).